Ovarian cancer causes the highest mortality rate among women with gynecologic malignancy, approximately 14,000 cancer deaths per year. Women with late-stage disease have a 2-year relapse rate of more than 50%, and a 5-year survival rate of less than 50%. The goal of this proposal is to identify the optimal configuration of a Listeria monocytogenes-based cancer vaccine encoding the tumor antigen mesothelin, for application as a targeted immunotherapy for ovarian cancer. Listeria is an intracellular bacterium that primes robust CD4+/CD8+ T-cell mediated responses, has striking potency in animal models of both infectious disease and cancer, and has been tested in healthy human volunteers. Mesothelin is a differentiation antigen that is expressed in 95% of ovarian cancers and lower levels in other cancers, but other than mesothelial cells, is not detected in diverse normal tissues, including normal ovaries. A panel of recombinant Listeria that express mesothelin fused to elements that augment antigen presentation will be derived, and tested for therapeutic efficacy in a newly-developed syngeneic mouse model that expresses mesothelin and recapitulates human ovarian cancer. Accomplishing these goals will set the stage in a Phase II SBIR for moving the project toward a clinical trial in women with advanced ovarian cancer.